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.. DO NOT EDIT THIS FILE, but the Thread.xml source instead.
.. The source is found in doc/classes or modules/<name>/doc_classes.

.. _class_Thread:

Thread
======

**Inherits:** :ref:`Reference<class_Reference>` **<** :ref:`Object<class_Object>`

A unit of execution in a process.

Description
-----------

A unit of execution in a process. Can run methods on :ref:`Object<class_Object>`\ s simultaneously. The use of synchronization via :ref:`Mutex<class_Mutex>` or :ref:`Semaphore<class_Semaphore>` is advised if working with shared objects.

**Note:** Breakpoints won't break on code if it's running in a thread. This is a current limitation of the GDScript debugger.

Tutorials
---------

- :doc:`../tutorials/performance/threads/using_multiple_threads`

- :doc:`../tutorials/performance/threads/thread_safe_apis`

- `3D Voxel Demo <https://godotengine.org/asset-library/asset/676>`__

Methods
-------

+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| :ref:`String<class_String>`           | :ref:`get_id<class_Thread_method_get_id>` **(** **)** |const|                                                                                                                                                               |
+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| :ref:`bool<class_bool>`               | :ref:`is_active<class_Thread_method_is_active>` **(** **)** |const|                                                                                                                                                         |
+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| :ref:`bool<class_bool>`               | :ref:`is_alive<class_Thread_method_is_alive>` **(** **)** |const|                                                                                                                                                           |
+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| :ref:`Error<enum_@GlobalScope_Error>` | :ref:`start<class_Thread_method_start>` **(** :ref:`Object<class_Object>` instance, :ref:`String<class_String>` method, :ref:`Variant<class_Variant>` userdata=null, :ref:`Priority<enum_Thread_Priority>` priority=1 **)** |
+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| :ref:`Variant<class_Variant>`         | :ref:`wait_to_finish<class_Thread_method_wait_to_finish>` **(** **)**                                                                                                                                                       |
+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

Enumerations
------------

.. _enum_Thread_Priority:

.. _class_Thread_constant_PRIORITY_LOW:

.. _class_Thread_constant_PRIORITY_NORMAL:

.. _class_Thread_constant_PRIORITY_HIGH:

enum **Priority**:

- **PRIORITY_LOW** = **0** --- A thread running with lower priority than normally.

- **PRIORITY_NORMAL** = **1** --- A thread with a standard priority.

- **PRIORITY_HIGH** = **2** --- A thread running with higher priority than normally.

Method Descriptions
-------------------

.. _class_Thread_method_get_id:

- :ref:`String<class_String>` **get_id** **(** **)** |const|

Returns the current ``Thread``'s ID, uniquely identifying it among all threads. If the ``Thread`` is not running this returns an empty string.

----

.. _class_Thread_method_is_active:

- :ref:`bool<class_bool>` **is_active** **(** **)** |const|

Returns ``true`` if this ``Thread`` has been started. Once started, this will return ``true`` until it is joined using :ref:`wait_to_finish<class_Thread_method_wait_to_finish>`. For checking if a ``Thread`` is still executing its task, use :ref:`is_alive<class_Thread_method_is_alive>`.

----

.. _class_Thread_method_is_alive:

- :ref:`bool<class_bool>` **is_alive** **(** **)** |const|

Returns ``true`` if this ``Thread`` is currently running. This is useful for determining if :ref:`wait_to_finish<class_Thread_method_wait_to_finish>` can be called without blocking the calling thread.

To check if a ``Thread`` is joinable, use :ref:`is_active<class_Thread_method_is_active>`.

----

.. _class_Thread_method_start:

- :ref:`Error<enum_@GlobalScope_Error>` **start** **(** :ref:`Object<class_Object>` instance, :ref:`String<class_String>` method, :ref:`Variant<class_Variant>` userdata=null, :ref:`Priority<enum_Thread_Priority>` priority=1 **)**

Starts a new ``Thread`` that runs ``method`` on object ``instance`` with ``userdata`` passed as an argument. Even if no userdata is passed, ``method`` must accept one argument and it will be null. The ``priority`` of the ``Thread`` can be changed by passing a value from the :ref:`Priority<enum_Thread_Priority>` enum.

Returns :ref:`@GlobalScope.OK<class_@GlobalScope_constant_OK>` on success, or :ref:`@GlobalScope.ERR_CANT_CREATE<class_@GlobalScope_constant_ERR_CANT_CREATE>` on failure.

----

.. _class_Thread_method_wait_to_finish:

- :ref:`Variant<class_Variant>` **wait_to_finish** **(** **)**

Joins the ``Thread`` and waits for it to finish. Returns the output of the method passed to :ref:`start<class_Thread_method_start>`.

Should either be used when you want to retrieve the value returned from the method called by the ``Thread`` or before freeing the instance that contains the ``Thread``.

To determine if this can be called without blocking the calling thread, check if :ref:`is_alive<class_Thread_method_is_alive>` is ``false``.

**Note:** After the ``Thread`` finishes joining it will be disposed. If you want to use it again you will have to create a new instance of it.

.. |virtual| replace:: :abbr:`virtual (This method should typically be overridden by the user to have any effect.)`
.. |const| replace:: :abbr:`const (This method has no side effects. It doesn't modify any of the instance's member variables.)`
.. |vararg| replace:: :abbr:`vararg (This method accepts any number of arguments after the ones described here.)`